STTR Phase II: Nano-Layered Composites as High-Temperature Hard Coatings

该小型企业技术转移(STTR)第二阶段项目旨在开发用于高温摩擦学应用的新型纳米层状涂层，特别是在高温(高达1000摄氏度)下性能良好的刀具涂层。人们对这些涂层有很高的兴趣，因为人们希望以更高的速度切割，并因为在加工过程中使用冷却剂而日益关注环境问题。传统的涂层材料在这些条件下表现不佳，主要是因为它们的硬度随着温度的上升而迅速下降。第一阶段的研究开发了一种新的涂层，将许多交替的纳米厚度的金属和氮化物层结合在一起，显示出显著的硬度提高。高温退火后硬度保持在44千兆卡(GPA)，证明了这些新材料作为高温稳定涂层的可行性。纳米层中强烈的位错约束可能会产生比整体涂层更高的高温硬度，从而提供更好的耐磨性。在第二阶段，将开发纳米层状涂层，以优化关键性能，包括硬度、与基材的热膨胀匹配、防止溶解到不同工件的稳定性和抗氧化性。纳米涂层刀具有可能使干切削成为一种实用的替代方法，并改善湿式加工性能。

This Small Business Technology Transfer (STTR) Phase II Project aims to develop novel nano-layered coatings for high-temperature tribological applications, specifically cutting-tool coatings that perform well at elevated temperatures (up to 1000 degrees C). There is a high level of interest in these coatings because of the desire to cut at higher rates and due to increasing environmental concerns over the use of coolants during machining. Traditional coating materials do not perform well under these conditions, primarily because their hardnesses decrease rapidly as temperature rises. Research in Phase I developed a new class of coatings, combining many alternating nanometer-thick layers of metals and nitrides, which show substantial hardness enhancements. Hardnesses up to 44 gigapascals (GPa) were maintained after high temperature annealing, demonstrating the feasibility of these new materials as high-temperature stable coatings. Strong dislocation confinement in nano-layers is likely to yield higher high-temperature hardness than in monolithic coatings, providing improved wear resistance. In Phase II, nano-layered coatings will be developed that optimize key properties including hardness, thermal expansion match with the substrate, stability against dissolution into different workpieces, and oxidation resistance. Nano-layered coated cutting tools have the potential to make dry-cutting a practical alternative, and to improve wet-machining performance.